Part 62

Gabbett’s counter-staining and decolorizing solution is especially useful in economizing time. After staining, as above directed, in the carbol-fuchsin solution for one minute, wash in water, then cover with a solution of 2 grams methylene blue (powder) in 100cc. of 10 per cent. sulphuric acid, until the film has a faintly bluish tint: then wash thoroughly in water and examine. Tubercle bacilli come out red, others blue.

In examination of tissues the microscopic sections are steeped for twenty-four hours in the carbol-fuchsin solution (or 1 hour at a temperature of 45° to 50° C.), then decolorized in a 5 per cent. sulphuric acid for a few seconds, then in a 70 per cent. alcohol: they are then counter-stained in an aqueous solution of methylene blue, washed in water dehydrated with absolute alcohol, cleared up in xyol or oil of cedar, and mounted in Canada balsam.

Biology. The bacillus tuberculosis is notorious for its variant forms, assumed in adapting itself to given environments, and which it retains with considerable tenacity for a time, even when placed in a new and different medium. It is largely held to be an obligatory parasite, and incapable of survival as a saprophyte, yet Straus, Nocard and others, have shown that the form obtained from the tuberculosis of birds can easily be made to live in suitable dead mixtures of organic matter. It is also notorious that the bacillus taken direct from the tubercle of the mammal, and which, as a rule, fails to grow at once in glycerined bouillon, yet, after a first successful culture in the new medium, often adapts itself completely, and thereafter it can in many cases be transferred from bouillon to bouillon, with as great certainty as it could formerly be inoculated from ox to ox. The difference is one of habit and adaptability, rather than any primary and permanent distinction of species. There is every reason to believe that the microbe has lived, and under given conditions can still be made to live as a saprophyte, with a greatly reduced adaptability to parasitic life in the animal, just as we see to-day that it is only with great difficulty transferred from certain genera of animals to certain other genera (from bird to ox and vice versa). Trudeau tells us of a culture of a bacillus tuberculosis from man, inoculated on the rabbit and then cultivated in vitro in successive generations for six years, that was in this way robbed of its pathogenesis for Guinea pigs, which, after inoculation, lived for many months, some two and a half years, and some even recovered. The average duration of life in the Guinea pig, after tuberculosis inoculation from man, rabbit, Guinea pig or recent culture is but seventeen days. The bacillus of human sputum often produces only localized tuberculosis in the ox. Even in the same species and individual the pathogenesis often varies materially. Nothing is more familiar than the slow progress of tuberculosis in the bones and lymph glands of man, on the one hand, and its frequently rapid progress in the lungs, liver and brain, on the other. As inoculated on the lower animals bacilli from the lungs of man are usually more virulent than those from the lymph glands (Creighton, Arloing, F. Craven Moore, Courmont and Denis). Among seven specimens of human sputum, the bacilli in six cases showed a fair average vitality, whereas those of the seventh failed to grow on blood serum of the dog (Theobald Smith). In both man and cow a large proportion of cases of tuberculosis remain localized, the disease lasting for years with little or no appreciable advancement, and not a few subjects appear to make a permanent recovery.

On every hand this evolutionary tendency of the bacillus tuberculosis places itself in evidence, demanding a recognition of the fact, that more or less transient or lasting variations in accordance with previous or existing environment, control to a large extent the transmissibility of the disease among different genera and even among individuals of the same genera and species, and also the fatal progress, or the mild and evanescent issue of the infection.

Even the most widely divergent of these evolutionary forms can often be made to approach each other and apparently merge into one type. Profiting by the example of Metchnikoff, Nocard enclosed in collodion capsules the bacilli of the human sputum and inserted the capsules into the peritoneal cavity of chickens which had proved refractory to their direct inoculation. This excluded the direct action of the leucocytes from the encapsuled bacilli, but allowed the endosmosis of the serum of the fowl for their nourishment. After a sojourn of four months or more they were transferred to other capsules and again enclosed in the peritoneum and after a second and third transference of this kind it was found that the bacillus had become actively pathogenic for the chicken, having acquired the infecting potencies of the bacillus of avian tuberculosis.

In keeping with the above is the fact that both rabbit and horse are easily infected by the bacillus obtained from birds, and that after a certain number of transmissions through the rabbit the issue of the bacilli of bird and mammal appear to become identical. No less instructive are the cases of the infection of carp by human sputa and the conveyance of tuberculosis to rabbits and Guinea pigs by inoculation with the nodules of the infected carp.

The vitality of bacillus tuberculosis is strong but variable. In sterilized water at 46° to 64° F. the human bacillus survived for fifty to seventy days (Chantemesse and Vidal), the bovine indefinitely (Galtier) and the avian bacillus at a higher temperature one hundred and seventeen days (Straus and DeBarry). In dried expectoration the bacillus of man still infects after nine or ten months (Koch, Schill, Fischer, De Thoma). In infected cow’s lung, dried and pulverized, it infected Guinea pigs at 102 days (Cadeac and Malet). In putrid matter it infected after 43 days (Schill, Fischer), 167 days (Cadeac and Malet), several years in a grave (Schottelius).

It is not destroyed by gastric juice (Fischer, Falk). The bacillus from tubercle of birds has a much greater vitality than that of mammals. Marfucci successfully seeded new media from a culture of two years old, and cultures in artificial media can be started more successfully.

Full sunlight renders sputum on a solid nonabsorbent surface noninfecting in several hours, varying according to the thickness of the layer (Koch, Straus). When sputum is mixed in soil it may survive until the 137th day (Feltz). On woolen cloth it may live five hours (Migneco).

Diffuse daylight, with shading from the sun, killed in seven days (Koch), to eighteen days (Lucibelli).

X-Rays do not arrest the growth of cultures (Blaikie, Pott, Ausset).

A dry temperature of 212° F. for an hour left some of the bacilli still infecting to Guinea pigs (Lartigan).

A moist heat of 140° F. for one hour sterilizes (De Man, Th. Smith, etc.). The scum formed on the milk may still prove infecting (Th. Smith). Half an hour of a moist temperature of 212° F. is sterilizing. Yet in the case of steaks, roasts and boiled meats the size of the piece often prevents the reaching of this temperature throughout, and it becomes unsafe to use any meat in which the redness of the juice shows, that the albumen has not all been fully coagulated (162° F.).

A freezing temperature, −16° to −26° F., does not devitalize the bacilli, even when alternated with thawing at intervals for several weeks (Galtier, Cadeac and Malet).

Heavy salting of meats has been thought to kill the bacillus in a month. After 15 days in salt the microbe failed to kill rabbits, but still killed the Guinea pig, whereas after 30 days it killed neither (Galtier). The fact that salted meats are always unequally impregnated in different parts, renders this extremely unreliable and more of a snare than a guide.

The action of chemical disinfectants varies not only with the agent but also with the medium in which the bacillus is found. In simple liquid media (bouillon) the following results were obtained:

Parts per 1000. Killed in. Carbolic Acid 50:1000 30″ (Yersin) „ „ 10:1000 1′ „ Alcohol (absolute) 1000:1000 5′ „ Ether 1000:1000 10′ „ Iodoform ether 10:1000 5′ „ Mercuric chloride 1:1000 10′ „ Salicylic acid 2.5:1000 6 hrs. „ Anilin water Saturated ———————— ——————— ———————— Thymol 3:1000 3 hrs. (Yersin) Formalin vapor 60:1000 40 hrs. (Murray) Sulphurous Acid (Sulphur 1 oz. to cubic metre) ————————— 14 hrs. (Vallin).

The following agents proved ineffective: Saturated aqueous solution of creosote, or of B-naphthol, of naphthalin, of potassium iodide, of potassium bromide:—bromine water, iodine water (1:500), iodoform solution or vapor, vapor of oil of turpentine.

ACCESSORY CAUSES OF TUBERCULOSIS IN ANIMALS.

While recognizing that in the absence of the tubercle bacillus there can be no tuberculosis yet we must not ignore the fact that many conditions of the animal system and its environment contribute largely to the propagation of the disease on the one hand, or to hinder its progress on the other. None of these conditions can call the germ into being de novo, but in its presence, they greatly favor its diffusion or even its malignancy. Like any other seed, this bacillus requires a suitable soil and favorable climate, to bring out its most destructive development. In striking the balance, we have to guard against the error of so many, who would attribute to the germ alone the deadly results and who assume that these should be the same under all conditions, and the opposite error no less prevalent, that ascribes the evil to the conditions, and holds that without these the germ would be harmless.

Hereditary Predisposition. Racial Vulnerability. Before the discovery of the specific bacillus, when as yet tuberculosis was held to result from a constitutional weakness, or cachexia in which deterioration of cells was held to be the main factor, the disease was held to be mainly hereditary, and its every day transmission in the line of descent, and the increasing mortality to extinction of given families were confidently appealed to in support of the doctrine. Now, however, we recognize that congenital tuberculosis in man or beast is very exceptional, and that the morbid process almost invariably takes its start from the germ implanted after birth. In Saxony when the tuberculous cows were 16.5 per cent. tuberculous calves were but .2 per cent., though the latter had been fattened on the milk of the former. In Munich but two calves were found tuberculous in 400,000 killed, and in Lyons but five in a similar number. Up to the present the number of calves recorded as tuberculous at birth does not exceed seventy.

That the young almost always contracted the disease, only after birth, virtually disposes of the alleged heredity of the tuberculosis but it by no means antagonizes the heredity of the racial vulnerability. As man, cattle, swine and Guinea pigs show a much greater vulnerability than the carnivora in general, so certain families in each of these genera show a more decided susceptibility to tuberculosis under similar conditions than do certain other families. This goes far to explain the appearance of tuberculosis, in certain lines of blood, and its advance to the extinction of the family, while under no better environment, other families can count on a practical immunity. In the Burden herd of Jerseys in 1877, I condemned eleven animals, verifying my diagnosis by necropsies, and found to my surprise that I had taken every representative, even the grades, of a given family, and left all the pure bred members of a second family untouched. Both families had mingled freely in the pastures and yards, yet the second family furnished no cases of tuberculosis then nor for many years afterward. The case is all the more striking that the non-tuberculous family gave the largest yield of milk and might have been expected to run down rather than the other on account of this drain.

Close Buildings. Lack of Ventilation. Air rendered impure by being breathed again and again, predisposes strongly to tuberculosis, and has been even looked upon as the sole cause (Macormac). Everywhere city dairy cows, kept in confined, close buildings, suffer severely (6 to 20 per cent. and upward); in Berlin 75 per cent. (Ostertag); in Denmark 61 per cent. (Bang), while in the same districts country cows are comparatively immune (often 1 to 2 per cent.), and steers raised in the open air still less (0.02 per cent. for our Plains cattle). For the slighter cases of tuberculosis in man and beast, life in a pure open air, day and night, in a genial climate, gives the best hope of improvement or recovery. In the Burden Jersey herd above referred to, animals condemned in spring as tuberculous, were turned out to pasture during the summer where they maintained an appearance of robust health, yet when returned to the barns in fall they fell off rapidly, so that some had to be helped to rise in the stall. “The stabled cow, the tame rabbit, the monkey, the caged lion, tiger or elephant are almost invariably cut off by scrofulous affection” (Aitken). It has long been noticed that sailors sleeping in close spaces (Bryson, Parkes), soldiers confined to close stone barracks even in the tropics (Parkes), suffer much more than the officers in more spacious rooms (Clark). Monks and nuns (two-thirds of the deaths, Leudet) occupying confined cells, and the inmates of prisons (four times the average outside, Baer) have shown an extraordinary prevalence of tuberculosis and attendant mortality. While this can be attributed mainly to the preservation and concentration of the bacillus in such places, a considerable allowance must be made for the impure and rebreathed air.

Dark, Foul, Damp Stables. Dark stables are usually close, dirty and damp as well, and all these conditions alike conduce to tuberculosis. Darkness hinders the development of organic coloring matter in living bodies, whether chlorophyll in plants or hæmoglobin in the blood of animals. Hæmoglobin is the main oxygen carrier in the blood, and in case of its deficiency the tissues are not properly ærated. The result is as if the inhaled air contained little oxygen, so that darkness further intensifies the evil of rebreathed, deoxygenated air. The extraordinary mortality from tubercle among prisoners, monks, nuns and miners serves to further accentuate this conclusion.

Trudeau’s experiment with rabbits is instructive in this connection. Of a number inoculated with the same number of tubercle bacilli, one half were kept in the open air and the rest in a dark, damp, underground place deprived of sunlight. When killed on the same day, it was found that the open air rabbits showed only slight lesions or none, while the underground lot had extensive tuberculosis.

The impure stable air lowers the vital tone of the animal, especially if the impurity has come from animal exhalations.

The same is true of damp air, “a damp ship is an unhealthy one,” and Bowditch and Buchanan pointed out the especial prevalence of tubercle in cold, damp, undrained, foggy localities. This does not hold for all damp lands, yet damp, fog, and cold are especially hurtful in presence of the germ.

INSUFFICIENT OR UNWHOLESOME FOOD.